The migration of lanthanide fission products to cladding materials is recognized as one of the key causes of fuel–cladding chemical interaction(FCCI) in metallic fuels during operation. We have performed first-princi...The migration of lanthanide fission products to cladding materials is recognized as one of the key causes of fuel–cladding chemical interaction(FCCI) in metallic fuels during operation. We have performed first-principles density functional theory calculations to investigate the segregation behavior of lanthanide fission products(La, Ce, Pr, and Nd) and their effects on the intergranular embrittlement at Σ3(111) tilt symmetric grain boundary(GB) in α-Fe. It is found that La and Ce atoms tend to reside at the first layer near the GB with segregation energies of-2.55 eV and-1.60 eV, respectively,while Pr and Nd atoms prefer to the core mirror plane of the GB with respective segregation energies of-1.41 eV and-1.50 eV. Our calculations also show that La, Ce, Pr, and Nd atoms all act as strong embrittlers with positive strengthening energies of 2.05 eV, 1.52 eV, 1.50 eV, and 1.64 eV, respectively, when located at their most stable sites. The embrittlement capability of four lanthanide elements can be determined by the atomic size and their magnetism characters. The present calculations are helpful for understanding the behavior of fission products La, Ce, Pr, and Nd in α-Fe.展开更多
The intermetallic compounds formation at interface between rare earth elements and clad material were investigated to demonstrate the effects of rare earth elements on fuel-cladding chemical interaction （FCCI） behav...The intermetallic compounds formation at interface between rare earth elements and clad material were investigated to demonstrate the effects of rare earth elements on fuel-cladding chemical interaction （FCCI） behavior. Mischmetal （70Ce-30La） and Nd were prepared as rare earth elements. Diffusion couple testing was performed on the rare earth elements and cladding （9Cr2W steel） near the operation temperature of （sodium-cooled fast reactor） SFR fuel. The performance of a diffusion barrier consisting of Zr and V metallic foil against the rare earth elements was also evaluated. Our results showed that Ce and Nd in the rare earth elements and Fe in the clad material interdiffused and reacted to form intermetallic species according to the parabolic rate law, describing the migration of the rare earth element. The diffusion of Fe limited the reaction progress such that the entire process was governed by the cubic rate law. Rare earth materials could be used as a surrogate for high burnup metallic fuels, and the performance of the barrier material was demonstrated to be effective.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.U1867217)the National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2019ZX06004009)the China National Nuclear Corporation Centralized Research and Development Project(Grant No.FY18000120)
文摘The migration of lanthanide fission products to cladding materials is recognized as one of the key causes of fuel–cladding chemical interaction(FCCI) in metallic fuels during operation. We have performed first-principles density functional theory calculations to investigate the segregation behavior of lanthanide fission products(La, Ce, Pr, and Nd) and their effects on the intergranular embrittlement at Σ3(111) tilt symmetric grain boundary(GB) in α-Fe. It is found that La and Ce atoms tend to reside at the first layer near the GB with segregation energies of-2.55 eV and-1.60 eV, respectively,while Pr and Nd atoms prefer to the core mirror plane of the GB with respective segregation energies of-1.41 eV and-1.50 eV. Our calculations also show that La, Ce, Pr, and Nd atoms all act as strong embrittlers with positive strengthening energies of 2.05 eV, 1.52 eV, 1.50 eV, and 1.64 eV, respectively, when located at their most stable sites. The embrittlement capability of four lanthanide elements can be determined by the atomic size and their magnetism characters. The present calculations are helpful for understanding the behavior of fission products La, Ce, Pr, and Nd in α-Fe.
基金Project supported by National Nuclear Technology Program of National Research Foundation (NRF)Ministry of Education, Science and Technology (MEST), Korean Government
文摘The intermetallic compounds formation at interface between rare earth elements and clad material were investigated to demonstrate the effects of rare earth elements on fuel-cladding chemical interaction （FCCI） behavior. Mischmetal （70Ce-30La） and Nd were prepared as rare earth elements. Diffusion couple testing was performed on the rare earth elements and cladding （9Cr2W steel） near the operation temperature of （sodium-cooled fast reactor） SFR fuel. The performance of a diffusion barrier consisting of Zr and V metallic foil against the rare earth elements was also evaluated. Our results showed that Ce and Nd in the rare earth elements and Fe in the clad material interdiffused and reacted to form intermetallic species according to the parabolic rate law, describing the migration of the rare earth element. The diffusion of Fe limited the reaction progress such that the entire process was governed by the cubic rate law. Rare earth materials could be used as a surrogate for high burnup metallic fuels, and the performance of the barrier material was demonstrated to be effective.
